The specific aims of the proposal are a) to characterize the expression of insulin-like growth factor (IGF) genes in fetal rat kidney and b) to define the role(s) of IGFs acting alone or in concert with other growth factors in embryonic kidney development. To these ends we will: 1) identify metanephric structures in thin sections of whole rat embryos at different stages in development; 2) Perform immunohistochemical staining of sections using antibodies directed against IGF I and IGF II to determine the localization of these peptides in metanephric kidney; 3) Perform in-situ hybridization of mRNAs for IGF I and IGF II in thin sections of rat embryos using specific radiolabeled probes for these mRNAs; 4) Characterize binding of 125I-IGF I, 125I-IGF II and 125 I-growth hormone to metanephroi; 5) Isolate metanephroi from rat embryos and culture these organs in defined media; 6) Determine whether IGF I or IGF II is produced by developing metanephric kidney in organ culture, and if so whether production is growth hormone-dependent; and 6) Determine the effect(s) of IGF I, IGF II, and polypeptide growth factors produced in adult kidney (epidermal growth factor, platelet-derived growth factor, transforming growth factor beta) on metanephrogenesis in vitro. These studies will utilize cellular and molecular biological techniques to define IGF gene expression in embryonic kidney. The data will provide insights into the role(s) of IGFs and/or other polypeptide growth factors in development of the metanephric kidney, and advance understanding of normal physiology and pathophysiology of renal development.